package org.simple.rpc.load.hash;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


/**
 *   一致性hash 算法 算生成者目标地址  源码来至jedis连接池，一致性hash问题可自行百度
 * @author wangbo
 *
 */
public interface Hashing {
	 Hashing MURMUR_HASH = new MurmurHash();
	  ThreadLocal<MessageDigest> md5Holder = new ThreadLocal<MessageDigest>();

	  Hashing MD5 = new Hashing() {
	    public long hash(String key) {
	      return hash(SafeEncoder.encode(key));
	    }

	    public long hash(byte[] key) {
	      try {
	        if (md5Holder.get() == null) {
	          md5Holder.set(MessageDigest.getInstance("MD5"));
	        }
	      } catch (NoSuchAlgorithmException e) {
	        throw new IllegalStateException("++++ no md5 algorithm found");
	      }
	      MessageDigest md5 = md5Holder.get();

	      md5.reset();
	      md5.update(key);
	      byte[] bKey = md5.digest();
	      long res = ((long) (bKey[3] & 0xFF) << 24) | ((long) (bKey[2] & 0xFF) << 16)
	          | ((long) (bKey[1] & 0xFF) << 8) | (long) (bKey[0] & 0xFF);
	      return res;
	    }
	  };

	  long hash(String key);

	  long hash(byte[] key);
}
